533 lines
12 KiB
C
533 lines
12 KiB
C
|
/*
|
||
|
* HX711: analog to digital converter for weight sensor module
|
||
|
*
|
||
|
* Copyright (c) 2016 Andreas Klinger <ak@it-klinger.de>
|
||
|
*
|
||
|
* This program is free software; you can redistribute it and/or modify
|
||
|
* it under the terms of the GNU General Public License as published by
|
||
|
* the Free Software Foundation; either version 2 of the License, or
|
||
|
* (at your option) any later version.
|
||
|
*
|
||
|
* This program is distributed in the hope that it will be useful,
|
||
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||
|
* GNU General Public License for more details.
|
||
|
*/
|
||
|
#include <linux/err.h>
|
||
|
#include <linux/kernel.h>
|
||
|
#include <linux/module.h>
|
||
|
#include <linux/of.h>
|
||
|
#include <linux/platform_device.h>
|
||
|
#include <linux/property.h>
|
||
|
#include <linux/slab.h>
|
||
|
#include <linux/sched.h>
|
||
|
#include <linux/delay.h>
|
||
|
#include <linux/iio/iio.h>
|
||
|
#include <linux/iio/sysfs.h>
|
||
|
#include <linux/gpio/consumer.h>
|
||
|
#include <linux/regulator/consumer.h>
|
||
|
|
||
|
/* gain to pulse and scale conversion */
|
||
|
#define HX711_GAIN_MAX 3
|
||
|
|
||
|
struct hx711_gain_to_scale {
|
||
|
int gain;
|
||
|
int gain_pulse;
|
||
|
int scale;
|
||
|
int channel;
|
||
|
};
|
||
|
|
||
|
/*
|
||
|
* .scale depends on AVDD which in turn is known as soon as the regulator
|
||
|
* is available
|
||
|
* therefore we set .scale in hx711_probe()
|
||
|
*
|
||
|
* channel A in documentation is channel 0 in source code
|
||
|
* channel B in documentation is channel 1 in source code
|
||
|
*/
|
||
|
static struct hx711_gain_to_scale hx711_gain_to_scale[HX711_GAIN_MAX] = {
|
||
|
{ 128, 1, 0, 0 },
|
||
|
{ 32, 2, 0, 1 },
|
||
|
{ 64, 3, 0, 0 }
|
||
|
};
|
||
|
|
||
|
static int hx711_get_gain_to_pulse(int gain)
|
||
|
{
|
||
|
int i;
|
||
|
|
||
|
for (i = 0; i < HX711_GAIN_MAX; i++)
|
||
|
if (hx711_gain_to_scale[i].gain == gain)
|
||
|
return hx711_gain_to_scale[i].gain_pulse;
|
||
|
return 1;
|
||
|
}
|
||
|
|
||
|
static int hx711_get_gain_to_scale(int gain)
|
||
|
{
|
||
|
int i;
|
||
|
|
||
|
for (i = 0; i < HX711_GAIN_MAX; i++)
|
||
|
if (hx711_gain_to_scale[i].gain == gain)
|
||
|
return hx711_gain_to_scale[i].scale;
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
static int hx711_get_scale_to_gain(int scale)
|
||
|
{
|
||
|
int i;
|
||
|
|
||
|
for (i = 0; i < HX711_GAIN_MAX; i++)
|
||
|
if (hx711_gain_to_scale[i].scale == scale)
|
||
|
return hx711_gain_to_scale[i].gain;
|
||
|
return -EINVAL;
|
||
|
}
|
||
|
|
||
|
struct hx711_data {
|
||
|
struct device *dev;
|
||
|
struct gpio_desc *gpiod_pd_sck;
|
||
|
struct gpio_desc *gpiod_dout;
|
||
|
struct regulator *reg_avdd;
|
||
|
int gain_set; /* gain set on device */
|
||
|
int gain_chan_a; /* gain for channel A */
|
||
|
struct mutex lock;
|
||
|
};
|
||
|
|
||
|
static int hx711_cycle(struct hx711_data *hx711_data)
|
||
|
{
|
||
|
int val;
|
||
|
|
||
|
/*
|
||
|
* if preempted for more then 60us while PD_SCK is high:
|
||
|
* hx711 is going in reset
|
||
|
* ==> measuring is false
|
||
|
*/
|
||
|
preempt_disable();
|
||
|
gpiod_set_value(hx711_data->gpiod_pd_sck, 1);
|
||
|
val = gpiod_get_value(hx711_data->gpiod_dout);
|
||
|
/*
|
||
|
* here we are not waiting for 0.2 us as suggested by the datasheet,
|
||
|
* because the oscilloscope showed in a test scenario
|
||
|
* at least 1.15 us for PD_SCK high (T3 in datasheet)
|
||
|
* and 0.56 us for PD_SCK low on TI Sitara with 800 MHz
|
||
|
*/
|
||
|
gpiod_set_value(hx711_data->gpiod_pd_sck, 0);
|
||
|
preempt_enable();
|
||
|
|
||
|
return val;
|
||
|
}
|
||
|
|
||
|
static int hx711_read(struct hx711_data *hx711_data)
|
||
|
{
|
||
|
int i, ret;
|
||
|
int value = 0;
|
||
|
int val = gpiod_get_value(hx711_data->gpiod_dout);
|
||
|
|
||
|
/* we double check if it's really down */
|
||
|
if (val)
|
||
|
return -EIO;
|
||
|
|
||
|
for (i = 0; i < 24; i++) {
|
||
|
value <<= 1;
|
||
|
ret = hx711_cycle(hx711_data);
|
||
|
if (ret)
|
||
|
value++;
|
||
|
}
|
||
|
|
||
|
value ^= 0x800000;
|
||
|
|
||
|
for (i = 0; i < hx711_get_gain_to_pulse(hx711_data->gain_set); i++)
|
||
|
hx711_cycle(hx711_data);
|
||
|
|
||
|
return value;
|
||
|
}
|
||
|
|
||
|
static int hx711_wait_for_ready(struct hx711_data *hx711_data)
|
||
|
{
|
||
|
int i, val;
|
||
|
|
||
|
/*
|
||
|
* a maximum reset cycle time of 56 ms was measured.
|
||
|
* we round it up to 100 ms
|
||
|
*/
|
||
|
for (i = 0; i < 100; i++) {
|
||
|
val = gpiod_get_value(hx711_data->gpiod_dout);
|
||
|
if (!val)
|
||
|
break;
|
||
|
/* sleep at least 1 ms */
|
||
|
msleep(1);
|
||
|
}
|
||
|
if (val)
|
||
|
return -EIO;
|
||
|
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
static int hx711_reset(struct hx711_data *hx711_data)
|
||
|
{
|
||
|
int ret;
|
||
|
int val = gpiod_get_value(hx711_data->gpiod_dout);
|
||
|
|
||
|
if (val) {
|
||
|
/*
|
||
|
* an examination with the oszilloscope indicated
|
||
|
* that the first value read after the reset is not stable
|
||
|
* if we reset too short;
|
||
|
* the shorter the reset cycle
|
||
|
* the less reliable the first value after reset is;
|
||
|
* there were no problems encountered with a value
|
||
|
* of 10 ms or higher
|
||
|
*/
|
||
|
gpiod_set_value(hx711_data->gpiod_pd_sck, 1);
|
||
|
msleep(10);
|
||
|
gpiod_set_value(hx711_data->gpiod_pd_sck, 0);
|
||
|
|
||
|
ret = hx711_wait_for_ready(hx711_data);
|
||
|
if (ret)
|
||
|
return ret;
|
||
|
/*
|
||
|
* after a reset the gain is 128 so we do a dummy read
|
||
|
* to set the gain for the next read
|
||
|
*/
|
||
|
ret = hx711_read(hx711_data);
|
||
|
if (ret < 0)
|
||
|
return ret;
|
||
|
|
||
|
/*
|
||
|
* after a dummy read we need to wait vor readiness
|
||
|
* for not mixing gain pulses with the clock
|
||
|
*/
|
||
|
ret = hx711_wait_for_ready(hx711_data);
|
||
|
if (ret)
|
||
|
return ret;
|
||
|
}
|
||
|
|
||
|
return val;
|
||
|
}
|
||
|
|
||
|
static int hx711_set_gain_for_channel(struct hx711_data *hx711_data, int chan)
|
||
|
{
|
||
|
int ret;
|
||
|
|
||
|
if (chan == 0) {
|
||
|
if (hx711_data->gain_set == 32) {
|
||
|
hx711_data->gain_set = hx711_data->gain_chan_a;
|
||
|
|
||
|
ret = hx711_read(hx711_data);
|
||
|
if (ret < 0)
|
||
|
return ret;
|
||
|
|
||
|
ret = hx711_wait_for_ready(hx711_data);
|
||
|
if (ret)
|
||
|
return ret;
|
||
|
}
|
||
|
} else {
|
||
|
if (hx711_data->gain_set != 32) {
|
||
|
hx711_data->gain_set = 32;
|
||
|
|
||
|
ret = hx711_read(hx711_data);
|
||
|
if (ret < 0)
|
||
|
return ret;
|
||
|
|
||
|
ret = hx711_wait_for_ready(hx711_data);
|
||
|
if (ret)
|
||
|
return ret;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
static int hx711_read_raw(struct iio_dev *indio_dev,
|
||
|
const struct iio_chan_spec *chan,
|
||
|
int *val, int *val2, long mask)
|
||
|
{
|
||
|
struct hx711_data *hx711_data = iio_priv(indio_dev);
|
||
|
int ret;
|
||
|
|
||
|
switch (mask) {
|
||
|
case IIO_CHAN_INFO_RAW:
|
||
|
mutex_lock(&hx711_data->lock);
|
||
|
|
||
|
/*
|
||
|
* hx711_reset() must be called from here
|
||
|
* because it could be calling hx711_read() by itself
|
||
|
*/
|
||
|
if (hx711_reset(hx711_data)) {
|
||
|
mutex_unlock(&hx711_data->lock);
|
||
|
dev_err(hx711_data->dev, "reset failed!");
|
||
|
return -EIO;
|
||
|
}
|
||
|
|
||
|
ret = hx711_set_gain_for_channel(hx711_data, chan->channel);
|
||
|
if (ret < 0) {
|
||
|
mutex_unlock(&hx711_data->lock);
|
||
|
return ret;
|
||
|
}
|
||
|
|
||
|
*val = hx711_read(hx711_data);
|
||
|
|
||
|
mutex_unlock(&hx711_data->lock);
|
||
|
|
||
|
if (*val < 0)
|
||
|
return *val;
|
||
|
return IIO_VAL_INT;
|
||
|
case IIO_CHAN_INFO_SCALE:
|
||
|
*val = 0;
|
||
|
mutex_lock(&hx711_data->lock);
|
||
|
|
||
|
*val2 = hx711_get_gain_to_scale(hx711_data->gain_set);
|
||
|
|
||
|
mutex_unlock(&hx711_data->lock);
|
||
|
|
||
|
return IIO_VAL_INT_PLUS_NANO;
|
||
|
default:
|
||
|
return -EINVAL;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
static int hx711_write_raw(struct iio_dev *indio_dev,
|
||
|
struct iio_chan_spec const *chan,
|
||
|
int val,
|
||
|
int val2,
|
||
|
long mask)
|
||
|
{
|
||
|
struct hx711_data *hx711_data = iio_priv(indio_dev);
|
||
|
int ret;
|
||
|
int gain;
|
||
|
|
||
|
switch (mask) {
|
||
|
case IIO_CHAN_INFO_SCALE:
|
||
|
/*
|
||
|
* a scale greater than 1 mV per LSB is not possible
|
||
|
* with the HX711, therefore val must be 0
|
||
|
*/
|
||
|
if (val != 0)
|
||
|
return -EINVAL;
|
||
|
|
||
|
mutex_lock(&hx711_data->lock);
|
||
|
|
||
|
gain = hx711_get_scale_to_gain(val2);
|
||
|
if (gain < 0) {
|
||
|
mutex_unlock(&hx711_data->lock);
|
||
|
return gain;
|
||
|
}
|
||
|
|
||
|
if (gain != hx711_data->gain_set) {
|
||
|
hx711_data->gain_set = gain;
|
||
|
if (gain != 32)
|
||
|
hx711_data->gain_chan_a = gain;
|
||
|
|
||
|
ret = hx711_read(hx711_data);
|
||
|
if (ret < 0) {
|
||
|
mutex_unlock(&hx711_data->lock);
|
||
|
return ret;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
mutex_unlock(&hx711_data->lock);
|
||
|
return 0;
|
||
|
default:
|
||
|
return -EINVAL;
|
||
|
}
|
||
|
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
static int hx711_write_raw_get_fmt(struct iio_dev *indio_dev,
|
||
|
struct iio_chan_spec const *chan,
|
||
|
long mask)
|
||
|
{
|
||
|
return IIO_VAL_INT_PLUS_NANO;
|
||
|
}
|
||
|
|
||
|
static ssize_t hx711_scale_available_show(struct device *dev,
|
||
|
struct device_attribute *attr,
|
||
|
char *buf)
|
||
|
{
|
||
|
struct iio_dev_attr *iio_attr = to_iio_dev_attr(attr);
|
||
|
int channel = iio_attr->address;
|
||
|
int i, len = 0;
|
||
|
|
||
|
for (i = 0; i < HX711_GAIN_MAX; i++)
|
||
|
if (hx711_gain_to_scale[i].channel == channel)
|
||
|
len += sprintf(buf + len, "0.%09d ",
|
||
|
hx711_gain_to_scale[i].scale);
|
||
|
|
||
|
len += sprintf(buf + len, "\n");
|
||
|
|
||
|
return len;
|
||
|
}
|
||
|
|
||
|
static IIO_DEVICE_ATTR(in_voltage0_scale_available, S_IRUGO,
|
||
|
hx711_scale_available_show, NULL, 0);
|
||
|
|
||
|
static IIO_DEVICE_ATTR(in_voltage1_scale_available, S_IRUGO,
|
||
|
hx711_scale_available_show, NULL, 1);
|
||
|
|
||
|
static struct attribute *hx711_attributes[] = {
|
||
|
&iio_dev_attr_in_voltage0_scale_available.dev_attr.attr,
|
||
|
&iio_dev_attr_in_voltage1_scale_available.dev_attr.attr,
|
||
|
NULL,
|
||
|
};
|
||
|
|
||
|
static struct attribute_group hx711_attribute_group = {
|
||
|
.attrs = hx711_attributes,
|
||
|
};
|
||
|
|
||
|
static const struct iio_info hx711_iio_info = {
|
||
|
.driver_module = THIS_MODULE,
|
||
|
.read_raw = hx711_read_raw,
|
||
|
.write_raw = hx711_write_raw,
|
||
|
.write_raw_get_fmt = hx711_write_raw_get_fmt,
|
||
|
.attrs = &hx711_attribute_group,
|
||
|
};
|
||
|
|
||
|
static const struct iio_chan_spec hx711_chan_spec[] = {
|
||
|
{
|
||
|
.type = IIO_VOLTAGE,
|
||
|
.channel = 0,
|
||
|
.indexed = 1,
|
||
|
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
|
||
|
.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
|
||
|
},
|
||
|
{
|
||
|
.type = IIO_VOLTAGE,
|
||
|
.channel = 1,
|
||
|
.indexed = 1,
|
||
|
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
|
||
|
.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
|
||
|
},
|
||
|
};
|
||
|
|
||
|
static int hx711_probe(struct platform_device *pdev)
|
||
|
{
|
||
|
struct device *dev = &pdev->dev;
|
||
|
struct hx711_data *hx711_data;
|
||
|
struct iio_dev *indio_dev;
|
||
|
int ret;
|
||
|
int i;
|
||
|
|
||
|
indio_dev = devm_iio_device_alloc(dev, sizeof(struct hx711_data));
|
||
|
if (!indio_dev) {
|
||
|
dev_err(dev, "failed to allocate IIO device\n");
|
||
|
return -ENOMEM;
|
||
|
}
|
||
|
|
||
|
hx711_data = iio_priv(indio_dev);
|
||
|
hx711_data->dev = dev;
|
||
|
|
||
|
mutex_init(&hx711_data->lock);
|
||
|
|
||
|
/*
|
||
|
* PD_SCK stands for power down and serial clock input of HX711
|
||
|
* in the driver it is an output
|
||
|
*/
|
||
|
hx711_data->gpiod_pd_sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_LOW);
|
||
|
if (IS_ERR(hx711_data->gpiod_pd_sck)) {
|
||
|
dev_err(dev, "failed to get sck-gpiod: err=%ld\n",
|
||
|
PTR_ERR(hx711_data->gpiod_pd_sck));
|
||
|
return PTR_ERR(hx711_data->gpiod_pd_sck);
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* DOUT stands for serial data output of HX711
|
||
|
* for the driver it is an input
|
||
|
*/
|
||
|
hx711_data->gpiod_dout = devm_gpiod_get(dev, "dout", GPIOD_IN);
|
||
|
if (IS_ERR(hx711_data->gpiod_dout)) {
|
||
|
dev_err(dev, "failed to get dout-gpiod: err=%ld\n",
|
||
|
PTR_ERR(hx711_data->gpiod_dout));
|
||
|
return PTR_ERR(hx711_data->gpiod_dout);
|
||
|
}
|
||
|
|
||
|
hx711_data->reg_avdd = devm_regulator_get(dev, "avdd");
|
||
|
if (IS_ERR(hx711_data->reg_avdd))
|
||
|
return PTR_ERR(hx711_data->reg_avdd);
|
||
|
|
||
|
ret = regulator_enable(hx711_data->reg_avdd);
|
||
|
if (ret < 0)
|
||
|
return ret;
|
||
|
|
||
|
/*
|
||
|
* with
|
||
|
* full scale differential input range: AVDD / GAIN
|
||
|
* full scale output data: 2^24
|
||
|
* we can say:
|
||
|
* AVDD / GAIN = 2^24
|
||
|
* therefore:
|
||
|
* 1 LSB = AVDD / GAIN / 2^24
|
||
|
* AVDD is in uV, but we need 10^-9 mV
|
||
|
* approximately to fit into a 32 bit number:
|
||
|
* 1 LSB = (AVDD * 100) / GAIN / 1678 [10^-9 mV]
|
||
|
*/
|
||
|
ret = regulator_get_voltage(hx711_data->reg_avdd);
|
||
|
if (ret < 0) {
|
||
|
regulator_disable(hx711_data->reg_avdd);
|
||
|
return ret;
|
||
|
}
|
||
|
/* we need 10^-9 mV */
|
||
|
ret *= 100;
|
||
|
|
||
|
for (i = 0; i < HX711_GAIN_MAX; i++)
|
||
|
hx711_gain_to_scale[i].scale =
|
||
|
ret / hx711_gain_to_scale[i].gain / 1678;
|
||
|
|
||
|
hx711_data->gain_set = 128;
|
||
|
hx711_data->gain_chan_a = 128;
|
||
|
|
||
|
platform_set_drvdata(pdev, indio_dev);
|
||
|
|
||
|
indio_dev->name = "hx711";
|
||
|
indio_dev->dev.parent = &pdev->dev;
|
||
|
indio_dev->info = &hx711_iio_info;
|
||
|
indio_dev->modes = INDIO_DIRECT_MODE;
|
||
|
indio_dev->channels = hx711_chan_spec;
|
||
|
indio_dev->num_channels = ARRAY_SIZE(hx711_chan_spec);
|
||
|
|
||
|
ret = iio_device_register(indio_dev);
|
||
|
if (ret < 0) {
|
||
|
dev_err(dev, "Couldn't register the device\n");
|
||
|
regulator_disable(hx711_data->reg_avdd);
|
||
|
}
|
||
|
|
||
|
return ret;
|
||
|
}
|
||
|
|
||
|
static int hx711_remove(struct platform_device *pdev)
|
||
|
{
|
||
|
struct hx711_data *hx711_data;
|
||
|
struct iio_dev *indio_dev;
|
||
|
|
||
|
indio_dev = platform_get_drvdata(pdev);
|
||
|
hx711_data = iio_priv(indio_dev);
|
||
|
|
||
|
iio_device_unregister(indio_dev);
|
||
|
|
||
|
regulator_disable(hx711_data->reg_avdd);
|
||
|
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
static const struct of_device_id of_hx711_match[] = {
|
||
|
{ .compatible = "avia,hx711", },
|
||
|
{},
|
||
|
};
|
||
|
|
||
|
MODULE_DEVICE_TABLE(of, of_hx711_match);
|
||
|
|
||
|
static struct platform_driver hx711_driver = {
|
||
|
.probe = hx711_probe,
|
||
|
.remove = hx711_remove,
|
||
|
.driver = {
|
||
|
.name = "hx711-gpio",
|
||
|
.of_match_table = of_hx711_match,
|
||
|
},
|
||
|
};
|
||
|
|
||
|
module_platform_driver(hx711_driver);
|
||
|
|
||
|
MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");
|
||
|
MODULE_DESCRIPTION("HX711 bitbanging driver - ADC for weight cells");
|
||
|
MODULE_LICENSE("GPL");
|
||
|
MODULE_ALIAS("platform:hx711-gpio");
|
||
|
|